1. Field of the Invention
The present invention relates to a pneumatic tire, more particularly to an improved bead profile which can improve resistance to displacement on a rim without deteriorating rim-mounting performance.
2. Description of the Related Art
As shown in FIG. 5, a bead portion (a) of a pneumatic tire comprises: a bead base (a1) with a heel diameter of Dp at the axially outer end thereof; and a bead core (c). The heel diameter Db, for example, has a smaller 0.7% than a rim-diameter (Dr) of a standard rim R so that the bead base (a1) is fastened onto a rim base Rb of the rim R tightly. Further, air filled up in the pneumatic tire forces the bead portion (a) to contact a rim flange Rf of the rim R. Thus, the tire is mounted on the rim tightly.
However, since the rim base Rb has an inclination of about 5 degrees with respect to the tire axial direction, the bead portion (a) tends to be displaced to the inside of the tire axial direction according to a decrease of the air. Further, if a side force is applied into the tire with such a condition, the bead portion (a) may be slipped on the rim base Rb, and then drop into rim well (not shown) of the rim R with getting over a hump Rb1.